Lead terminal and power supply device

ABSTRACT

A power supply apparatus in which a battery and a circuit wiring board or boards are electrically connected by using lead terminals. The lead terminal is adapted so that thickness of a welding portion is caused to be thinner than the thickness of a conductive portion. Thus, current for welding flows to much degree in a thickness direction so that electric resistance of the welding portion becomes large, and heat based on the electric resistance also becomes large. From this fact, welding nugget can be enlarged. As the result of the fact that large welding nugget is formed, the lead terminals are welded to terminal portions of the battery with high reliability.

TECHNICAL FIELD

The present invention relates to a lead terminal connected to aconnected body with sufficient strength, and a power supply apparatusadapted for electrically connecting a battery and a circuit wiring boardor boards by using such a lead terminal or terminals.

This Application claims priority of Japanese Patent Application No.2003-015167, filed on Jan. 23, 2003, the entirety of which isincorporated by reference herein.

BACKGROUND ART

Hitherto, as a power supply of an electronic equipment such as note typepersonal computer, mobile telephone, camera integrated type VTR (VideoTape Recorder) and/or PDA (Personal Digital Assistants), etc., a lightsecondary battery having high energy density is required. As thesecondary battery having high energy density of this kind, there islithium ion secondary battery having energy density larger than that ofaqueous electrolyte battery, e.g., lead battery, nickel-cadmium batteryand/or nickel-hydrogen battery, etc.

The lithium ion secondary battery includes, e.g., a battery elementhaving cathode and anode, an armored can which is a cylindrical vesselhaving bottom portion for accommodating the battery element therewithin,and which is electrically connected to the anode so that the armored canserves as anode terminal, and a cover body adapted for closing theopening portion of the armored can and electrically connected to thecathode so that the cover body serves as an external cathode terminal.In the lithium ion secondary battery, as the result of the fact thatcover body is press-fitted into the opening portion of the armored canthrough gasket thereafter to caulk the opening portion of the armoredcan so that the cover body is fixed to close the opening portion of thearmored can, the battery element is hermetically sealed into the armoredcan. For this reason, in the lithium ion secondary battery, the armoredcan of the external anode terminal and the cover body of the externalcathode terminal are placed in insulating state by gasket.

In the case where the lithium ion secondary battery of such aconfiguration is used as a power supply of the above-describedelectronic equipments, the lithium ion secondary battery is mounted atthe electronic equipment in the state of battery pack. As the batterypack, there is a battery pack described in the Japanese PatentApplication Laid Open No. 2002-343320 publication.

In the battery pack 100, as shown in FIG. 1, e.g., two lithium ionsecondary batteryies 101 are accommodated within a pair of accommodatingcases 103 in the state connected to a circuit wiring board 102 forperforming over-charge protection, over-discharge protection and/orcharge/discharge control, etc. with respect to the battery. In concreteterms, the lithium ion secondary batteries 101 are connected to thecircuit wiring board 102 in series state through belt-shaped leadterminals 104 consisting of conductive metal, etc., e.g., nickel, ironor stainless steel, etc. At this time, in the battery pack 100, e.g.,connection between the armored can 105 serving as external terminaland/or the cover body 106 in the lithium ion secondary battery 101 andthe lead terminals 104 is performed by using the resistance weldingmethod.

As shown in FIG. 2, this resistance welding method is a method ofwelding the lead terminal 104 and the cover body 106 by making use ofheat by electric resistance produced between the lead terminal 104 andthe cover body 106 in allowing current of about 1200 A to flow from oneside of a pair of electrode rods 107, 108 disposed on the principalsurface of the lead terminals 104 to the other side electrode rodsthereof in the state where, e.g., lead terminal 104 is caused to be incontact with the cover body 106, etc.

In the case of welding lead terminals 104 with respect to the armoredcan 105 and/or the cover body 106 by such a method, it is necessary tothin thickness of the lead terminal 104 to a certain degree. In concreteterms, if the thickness of the lead terminal 104 consisting ofconductive metal, etc. e.g., nickel or iron, etc. is not caused to beequal to about 0.15 mm, it becomes difficult to perform welding in whichwelding reliability has been enhanced.

The reason thereof is as follows. As shown in FIG. 3, in the case where,e.g., lead terminal 104 having thickness of about 0.2 mm is used,because the thickness of the lead terminal 104 is too thick, a currentflowing in the lead terminal 104, so called reactive current at a pathindicated by arrow X in FIG. 3 would take place at a portion of currentflowing in the electrode rod 108 from the electrode rod 107 inperforming resistance welding.

For this reason, in the welding between the lead terminal 104 and thearmored can 105 or the cover body 106, current at a path indicated byarrow Y in FIG. 3, i.e., current flowing in a thickness direction of thelead terminal 104 to reach the armored can 105 or the cover body 106, socalled active current is decreased so that calorific value by electricresistance of the lead terminal 104 is reduced. Thus, in welding betweenthe lead terminal 104 and the armored can 105 or the cover body 106,there are instances where welding blocks, so-called welding nuggets 109formed as the result of the fact that the lead terminal 104 and thearmored can 105 or the cover body 106 are molten with each other by heatof electric resistance by active current of the lead terminal 104 isreduced so that welding strength may be weakened.

Particularly, in the case where lead terminal 104 is formed byconductive metal, etc. containing, e.g., copper, silver or aluminum,etc. having electric resistance smaller than that of the armored can 105or the cover body 106, ratio of reactive current becomes large amongcurrent flowing in the electrode rod 108 from the electrode rod 107 tothe electrode rod 108. As a result, welding strength between the leadterminal 104 and the armored can 105 or the cover body 106 is furtherweakened.

In such lithium ion secondary battery 101, in the case where, e.g., thebattery pack 100 is erroneously fallen down in detaching it fromelectronic equipment, etc. so that the lithium ion secondary battery 101undergoes impact, etc., because welding strength between the leadterminal 104 and the armored can 105 or the cover body 106 is weak,there are instances where connection between the lead terminal 104 andthe armored can 105 or the cover body 106 is broken to allow the batterypack 100 to be brough into unusable (unavailable) state.

Moreover, in the battery pack 100, in the case where the lead terminal104 is thinned for the purpose of enhancing welding reliability withrespect to the armored can 105 and/or the cover body 106, electricresistance of current flowing in a length direction in the lead terminal104 in charging/discharging the lithium ion secondary battery 101 wouldbecome large. For this reason, in the battery pack 100, there areinstances where the lead terminal 104 having large electric resistancemay be heated by current of charge/discharge operation so that thelithium ion secondary battery 101 is deteriorated by such heat. Namely,in the battery pack 100, it becomes difficult to use the lithium ionsecondary battery 101 as a power supply of recent electronic equipmentscaused to further have high function and high performance so that thereis required large current discharge in which discharge operation isperformed at current of about 1 C to 2 C per battery.

Further, in such lead terminal, because electric resistance is large,voltage drop takes place in the lithium ion secondary battery 101 at thetime of charge or discharge operation. As a result, power loss takesplace, leading to lowering of energy utilization efficiency.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a novel lead terminaland a power supply apparatus using such a lead terminal or terminals,which can solve problems that prior arts as described above have.

Another object of the present invention is to provide a lead terminalwelded to a connected body with suitable connection strength and havingsuppressed electric resistance.

A further object of the present invention is to provide a power supplyapparatus having enhanced (improved) connection reliability betweenbattery and lead terminal, and excellent in large current loadcharacteristic.

The lead terminal according to the present invention is directed to alead terminal for electrically connecting a first connected body and asecond connected body, the leading terminal being a plate terminalconsisting of conductive metal, the leading terminal including a weldingportion in which electricity (current) is caused to flow in the statecaused to be in contact with an external terminal of the first connectedbody so that the welding portion is resistance-welded to the externalterminal of the first connected body, a connecting portion connected toan external terminal of the second connected body, and a conductiveportion positioned between the welding portion and the connectingportion, and serving to allow the welding portion and the connectingportion to electrically conduct, wherein the lead terminal is formed sothat the thickness of the welding portion is thinner than the thicknessof the conductive portion.

In this lead terminal, since the welding portion which isresistance-welded to the external terminal of the first connected bodyis thinner than the conductive portion, it is possible to allow largepart of current flowing in the welding portion in welding the externalterminal of the first connected body and the welding portion to flow inthickness direction of the welding portion.

In the lead terminal according to the present invention, current forresistance-welding flows to much degree in thickness direction of thewelding portion so that electric resistance of the welding portion isincreased. As a result, calorific value produced at the contact portionbetween the external terminal of the first connected body and thewelding portion becomes large. Thus, it is possible to performresistance-welding of the welding portion with respect to the externalterminal of the first connected body with high welding strength.

In this lead terminal, since current for resistance-welding flows tomuch degree in thickness direction of the welding portion so thatelectric resistance of the welding portion becomes large, heat producedat the welding portion becomes large by increased electric resistance.Thus, it is possible to perform resistance-welding of the weldingportion with respect to the external terminal of the first connectedbody with high welding strength.

In the lead terminal according to the present invention, since theconductive portion is caused to be thicker than the welding portion, itis possible to suppress electric resistance between the welding portionand the connecting portion, which is produced when current is caused toflow in the conductive portion, i.e., electric resistance of theconductive portion.

The power supply apparatus according to the present invention comprisesa battery, a circuit wiring board for controlling charge and/ordischarge operation of the battery, and a lead terminal or terminals forelectrically connecting the battery and the circuit wiring board, thelead terminal being a plate material consisting of conductive metal, thelead terminal including a welding portion in which electricity is causedto flow in the state caused to be in contact with the external terminalof the battery so that the welding portion is resistance-welded to anexternal terminal of the battery, a connecting portion connected to theexternal terminal of the circuit wiring board, and a conductive portionpositioned between the welding portion and the connecting portion andserving to allow the welding portion and the connecting portion toelectrically conduct, wherein the lead terminal is formed so that thethickness of the welding portion is thinner than the thickness of theconductive portion.

In this power supply apparatus, since the welding portion of the leadterminal is thinner than the conductive portion, it is possible to allowlarge part of current flowing in the welding portion of the leadterminal in performing resistance-welding of the external terminal ofthe battery and the welding portion of the lead terminal to flow in athickness direction of the lead terminal.

In the power supply apparatus according to the present invention,current for resistance-welding flows to much degree in a thicknessdirection of the lead terminal so that electric resistance of thewelding portion is increased. As a result, calorific value produced atthe contact portion between the external terminal of the battery and thewelding portion of the lead terminal also becomes large. Thus, it ispossible to suitably resistance-weld the welding portion of the leadterminal to the external terminal of the battery with high weldingstrength.

In this power supply apparatus, since the conductive portion at the leadterminal is thicker than the welding portion, it is possible to suppresselectric resistance between the welding portion and the connectingportion, which is produced when electricity for charging/discharging thebattery is caused to flow in the lead terminal, i.e., electricresistance of the conductive portion. Accordingly, electric resistanceof the conductive portion at the lead terminal is suppressed, therebymaking it possible to suppress heat of the lead terminal by electricresistance when electricity is caused to flow in the lead terminal.

In addition, in the power supply apparatus according to the presentinvention, electric resistance of the lead terminal is suppressed sothat voltage drop and power loss at the time of charge/dischargeoperation can be reduced. Thus, the charge/discharge efficiency ispermitted to be satisfactory.

Still further objects of the present invention and practical meritsobtained by the present invention will become more apparent from theembodiments which will be given below with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing a conventional batterypack.

FIG. 2 is a perspective view showing the state where lead terminal iswelded to lithium ion secondary battery constituting the battery pack.

FIG. 3 is an essential part cross sectional view showing, in a modelform, the state where current for performing resistance welding flows inlead terminal provided at the battery pack.

FIG. 4 is a perspective view showing battery pack using lead terminalaccording to the present invention.

FIG. 5 is an exploded perspective view showing battery pack.

FIG. 6 is a perspective view showing battery module constituting thebattery pack.

FIG. 7 is an essential part cross sectional view showing an example oflead terminal provided at the battery pack.

FIG. 8 is an essential part cross sectional view showing connectingportion between lead terminal and battery.

FIG. 9 is a perspective view showing internal structure of the batteryconstituting battery pack.

FIG. 10 is a perspective view showing a resistor-welding machine usedfor connecting lead terminal and battery.

FIG. 11 is a view for explaining a method of connecting lead terminal tothe battery, and is a perspective view showing the state where thebattery is mounted at welding head.

FIG. 12 is a view for explaining a method of connecting lead terminal tothe battery, and is a perspective view showing the state where leadterminal is welded to the battery.

FIG. 13 is a view for explaining a method of connecting lead terminal tothe battery, and is an essential part cross sectional view showing, in amodel form, the state where current for resistance-welding flows in leadterminal.

FIG. 14 is a perspective view showing the state where slit is providedat lead terminal, and the battery is welded to the lead terminal.

FIG. 15 is an essential part cross sectional view showing, in a modelform, the state where slit is provided at lead terminal, and current forresistance-welding flows in the lead terminal.

FIG. 16 is a perspective view showing the state where welding portion oflead terminal is formed to be diamond-shaped.

FIG. 17 is a perspective view showing the state where bent portion isprovided at the lead terminal.

FIG. 18 is a perspective view showing the state where lead terminal isbent at the bent portion.

FIG. 19 is a perspective view showing another example of the leadterminal.

FIG. 20 is a perspective view showing a further example of the leadterminal.

FIG. 21 is a perspective view showing a still further example of thelead terminal.

FIG. 22A is a perspective view showing a still more further example ofthe lead terminal, and FIG. 22B is an essential part cross sectionalview thereof.

FIG. 23 is an exploded perspective view perspectively showing a portionof another example of battery pack according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A lead terminal and a power supply apparatus using such a lead terminalaccording to the present invention will now be explained with referenceto a battery pack 1 shown in FIGS. 4 and 5. The battery pack 1 is loadedwith respect to a loading portion provided at electronic equipment,etc., e.g., camera integrated type VTR, etc. to have ability to stablydeliver power of a predetermined voltage to the electronic equipment,etc.

Further, the battery pack 1 includes a pair of substantially cylindricalbatteries 2 a, 2 b which serve as power generating element, leadterminals 3 connected to external terminals of the pair of batteries 2a, 2 b, and a circuit wiring board 4 electrically connected to the pairof batteries 2 a, 2 b through the lead terminals 3 to thereby performcontrol of charge/discharge operation with respect to the pair ofbatteries 2 a, 2 b, wherein the pair of batteries 2 a, 2 b, the leadterminals 3 and the circuit wiring board 4 are accommodated within asubstantially box-shaped accommodating case 5.

The battery pack 1 is accommodated in the state where a battery module 6in which the pair of batteries 2 a, 2 b are connected in parallel by thelead terminals 3 so that they are integrated is connected to the circuitwiring board 4 through the lead terminals 3. It is to be noted thatwhile the battery module 6 in which the pair of batteries 2 a, 2 b areconnected in parallel will be explained here, the present invention isnot limited to such an implementation, but, e.g., battery module inwhich a pair of batteries 2 a, 2 b are connected in series may beemployed, and the number of batteries and/or arrangement thereof, etc.may be arbitrarily selected.

In the following explanation, in the case where either one of batteries2 a, 2 b is indicated, such battery is simply labeled as battery 2.

As shown in FIG. 6, lead terminal 3 constituting the battery module 6 isa plate material consisting of conductive metal, and includes pluralwelding portions 3 a connected to both end surfaces serving as externalterminals of the pair of batteries 2 a, 2 b, connecting portions 3 bconnected to connecting lands 7, etc. of the circuit wiring board 4, andconductive portions 3 c disposed between these welding portions 3 a andbetween the welding portion 3 a and the connecting portion 3 b andserving to allow these components to electrically conduct.

The lead terminal 3 is formed by conductive metal such as alloycontaining any one kind or plural kinds of e.g., nickel, nickel alloy,iron, iron alloy, stainless steel, zinc, zinc alloy, copper, copperalloy, sliver, silver alloy, gold, gold alloy, platinum, platinum alloy,aluminum, aluminum alloy, molybdenum, molybdenum alloy, tungsten,tungsten alloy, titanium, titanium alloy, beryllium, beryllium alloy,rhodium, and rhodium alloy.

The lead terminals 3 are adapted so that welding portions 3 a arerespectively welded to the same poles positioned on both end surfaces ofthe pair of batteries 2 a, 2 b to thereby integrate the pair ofbatteries 2 a, 2 b to constitute the battery module 6. In concreteterms, respective one end surfaces of the pair of batteries 2 a, 2 b areconnected in parallel by means of one lead terminal 3 byresistance-welding, and respective other end surfaces of the pair ofbatteries 2 a, 2 b are connected in parallel by means of one leadterminal 3 by resistance-welding to thereby constitute the batterymodule 6. In this example, in the battery module 6, since end surfacesof the pair of batteries 2 and welding portions 3 a areresistance-welded by the resistance welding method, it is possible toprevent battery deterioration taking place as the result of the factthat, e.g., in the case where welding is performed by ultrasonicwelding, etc., ultrasonic wave is transmitted to the battery. Thus, itis possible to suppress manufacturing cost as compared to laser welding,etc. in which the apparatus therefor is expensive.

In the battery module 6 constituted in this way, since lead terminals 3are respectively welded to both end surfaces of the pair of batteries 2a, 2 b, the pair of batteries 2 a, 2 b in which rotation in outercircumferential direction of the battery 2 has been prevented are fixedin the state where they are adjacent to each other. Moreover, the leadterminals 3 are adapted so that connecting portions 3 b are welded toconnecting lands 7, etc. of the circuit wiring board 4 by, e.g.,soldering, etc. to electrically connect the circuit wiring board 4 andthe pair of batteries 2 a, 2 b.

In the lead terminal 3, the thickness of substantially rectangularwelding portion 3 a is caused to be thinner than the thickness of theconductive portion 2 c. In concrete terms, the thickness of the weldingportion 3 a is thinned down to about 0.15 mm with respect to theconductive portion 3 c having thickness of about 0.3 mm.

For this reason, in the lead terminal 3, since welding portions 3 arespectively welded to both end surfaces serving as external terminalsof the pair of batteries 2 a, 2 b by the resistance-welding method, etc.are thinner than those of the conductive portions 3 c, large part ofcurrent for welding flowing in the welding portion 3 a in welding theend surfaces of the battery 2 and the welding portion 3 a is permittedto flow in a thickness direction of the welding portion 3 a.

Accordingly, in the lead terminal 3, current for welding flows in thethickness direction of the welding portion 3 a to much degree so thatelectric resistance of the welding portion 3 a is increased. As aresult, calorific value produced between the end surface of the battery2 and the welding portion 3 a also becomes large. Thus, the weldingportion 3 a is welded to the end surface of the battery 2 with highwelding strength.

In this example, in the lead terminal 3, etching processing, etc. isimplemented in the state where portions except for the portion where thewelding portion 3 a is provided is masked so that welding portion 3 ahaving thin thickness is provided. In the lead terminal 3, the timerequired for immersing it into etchant, etc. is controlled, therebypermitting the welding portion 3 a to have a predetermined thickness. Inthe lead terminal 3, there may be provided welding portion 3 a of whichthickness has been thinned by method, e.g., laser processing, and/ordrawing processing, etc. in addition to etching processing, etc.

In the lead terminal 3, while the welding portion 3 a may be constitutedby recessed portions provided at positions opposite to each other atboth principal surfaces of plate material consisting of conductive metalas shown in FIG. 7, one principal surface of the welding portion 3 a iscaused to be flat plane surface having no offset as shown in FIG. 8, forexample, to perform welding in such a manner to opposite the flatsurface to both end surfaces of the battery 2, thereby making itpossible to suitably resistance-weld the welding portion 3 a to the endsurface of the battery 2 without producing gap between the weldingportion 3 a and the battery 2.

In the lead terminal 3, since the conductive portion 3 c forelectrically conducting the welding portion 3 a welded to the battery 2and the connecting portion 3 b connected to the circuit wiring board 4is caused to be thicker than the welding portion 3 a, whereby whencurrent for changing/discharging the battery 2 is caused to flow,electric resistance produced between the welding portion 3 a and theconnecting portion 3 b, i.e., electric resistance of the conductiveportion 3 c is suppressed. Accordingly, in the lead terminal 3, sinceelectric resistance of the conductive portion 3 c is suppressed, even inthe case where large current of the order of 1 C to 2 C is caused toflow by, e.g., requirement of electronic equipment, etc., calorificvalue by electric resistance can be reduced. In this case, in the leadterminal 3, e.g., thickness of the conductive portion 3 c is permittedto be thick so that its thickness is equal to about 1 mm to 2 mm.

At the circuit wiring board 4 to which the battery module 6 is connectedthrough the lead terminals 3, pattern wiring (not shown) havingconnecting land 7 consisting of conductive metal, etc. and adapted sothat lead terminal 3 is connected by soldering, etc. electronic circuitcomponents (parts) such as IC (Integrated Circuit) chip and/or LSI(Large-Scale Integrated circuit) chip, etc. (not shown) connected to thepattern wiring and serving to perform charge/discharge control, and/orover-discharge and/or over-charge protection, etc., with respect to thebattery module 6 and/or protection element components (parts) such astemperature fuse, etc. are provided on a board 8.

Moreover, at the circuit wiring board 4, a connector 9 electricallyconnected to the pattern wiring, etc. by, e.g., soldering, etc. isattached to the other principal surface of the side opposite to oneprincipal surface where electronic circuits, etc. are attached. When thepower supply pack 1 is connected to electronic equipments, etc., theconnector 9 is engaged with external terminal, etc. provided atelectronic equipment, etc. so that it is electrically connected theretoto thereby function as a supply port for supplying electricity toelectronic equipment, etc. When the battery module 6 is charged, theconnector 9 also functions as a connecting portion to which, e.g., ACpower supply, etc. is connected. The circuit wiring board 4 isaccommodated within an accommodating case 5 in a manner along the sidewall of the accommodating case 5 in the state where, e.g., the side wallof substantially boxed-shaped accommodating case 5 and the otherprincipal surface of the board 8 are opposite to each other.

The accommodating case 5 within which the battery module 6 and thecircuit wiring board 4 are accommodated consists of insulating resin,etc., e.g., polycarbonate or ABS (Acrylonitrile Butadiene Styrene)resin, etc., and is composed of an upper case 10 and a lower case 11.The upper case 10 and the lower case 11 respectively have shapes inwhich side wall is provided in a projected manner along the outercircumferential edge portion of substantially rectangular principalsurface, and is constituted as substantially box-shaped accommodatingcase 5 by butting respective side walls with each other.

At the accommodating case 5, an opening portion for allowing theconnector 9 attached to the circuit wiring board 4 to be exposed towardthe external is formed by cut portions 12 formed at the side walls ofthe upper case 10 and the lower case 11, and an engagement recessedportion 13 with which the connector 9 is engaged.

At the lower case 11 of the accommodating case 5, there is provided abattery partition wall 14 for partitioning the surface of the side wherethe battery module 6 is accommodated into two parts. Further, at theaccommodating case 5, a pair of batteries 2 a, 2 b within the batterymodule 6 are respectively accommodated into two spaces partitioned bythe battery partition wall 14. Thus, the battery partition wall 14 iscaused to intervene therebetween so that it can be prevented that thebatteries 2 a, 2 b collide with each other therewithin.

At the lower case 11 of the accommodating case 5, plural holding pieces15 in which the battery holding pieces are caused to come into contactwith the outer circumferential surface of the battery 2 to thereby holdthe battery module 6 are provided at the face of the side where thebattery module 6 is accommodated in addition to the above-describedbattery partition walls 14. At the lower case 11, plural battery holdingpieces 15 are provided at the entirety of two spaces partitioned by thebattery partition wall 14, and are adapted so that contact surfaces 15 ahaving curve along the outer circumferential surface of the battery 2 ofthe battery holding pieces 15 come into contact with the outercircumferential surface of the battery 2 to thereby suitably hold thebattery module 6. It is to be noted, in the accommodating case 5, thebattery module 6 may be adhered (bonded) to the inner wall by adhesivemember, e.g., adhesive agent, etc. to thereby firmly fix the batterymodule 6.

Thus, in the power supply pack 1, it becomes possible to accommodate thebattery module 6 thereinto without shaking by the battery partition wall14 and the battery holding pieces 15 provided within the accommodatingcase 5.

In the case where the power supply pack 1 undergoes impact from theexternal, e.g., the power supply pack 1 is erroneously fallen down,since the battery partition wall 14 caused to intervene between a pairof batteries 2 a, 2 b at the battery module 6 function as buffermaterial, it is possible to suppress shape deformation of the battery 2and/or battery characteristic deterioration, etc. which take place asthe result of the fact that the batteries 2 a, 2 b collide with eachother. In addition, the battery partition wall 14 and/or the batteryholding piece 15 function in a manner to enhance rigidity of theaccommodating case 5.

Within the power supply pack 1 of such a configuration, there is alsoaccommodated, e.g., an insulator 16 for insulation, etc. for preventingcontact between the battery module 6 and the circuit wiring board 4 inaddition to the above-described battery module 6 and the circuit wiringboard 4, etc.

The insulator 16 consists of sheet-shaped insulating material, etc.,e.g., polyethylene, polypropylene or imcombustible (non-combustible)paper, etc., and is disposed between the battery module 6 and thecircuit wiring board 4. Thus, when, e.g., the power supply pack 1undergoes impact from the external, the insulator 16 prevents thebattery module 6 from coming into with the circuit wiring board 4. Fromthis fact, it is possible to prevent external short, etc. of the battery2, which takes place as the result of the fact that the battery module 6comes into contact with the circuit wiring board 4.

In addition, at the power supply pack 1, there is attached, at the outercircumference of the accommodating case 5, a label 17 in which, e.g.,manufacturing lot number, etc. is indicated to thereby permit source ofthe source battery module 6 and/or the circuit wiring board 4, etc. tobecome apparent.

Then, the battery 2 accommodated into the power supply pack 1constituted as described above will be explained. The battery 2includes, as shown in FIG. 9, a battery element 20 for generatingelectricity, an electrolytic solution 21 for moving ions within thebattery element 20, an armored can 22 for accommodating the batteryelement 20 and the electrolytic solution 21, and a cover body 23 forclosing the opening portion of the armored can 22.

The battery element 20 is caused to be of the configuration in which abelt-shaped cathode 24 using lithium transition metal compound oxide,etc. as active cathode material and a belt-shaped anode 25 usingcarbonaceous material, etc. as active anode material are laminatedthrough a belt-shaped separator 26 for shielding the cathode and theanode with each other so that they are not in contact with each other,and are wound in length direction. The battery 2 in which such batteryelement 20 serves as power generating element is so-called lithium ionsecondary buttery in which lithium ions are caused to be transferredbetween the cathode 24 and the anode 25 so that battery reaction isperformed.

The cathode 24 is caused to be of the structure in which cathodecompounding agent coating liquid containing active cathode material andbinding agent is coated, dried and pressurized with respect to theprincipal surface of a cathode collector 27 so that a cathodecompounding agent layer 28 is compressed and formed on the principalsurface of the cathode collector 27. A cathode terminal 29 of thecathode 24 is electrically connected to a predetermined position of thecathode collector 27. As the cathode terminal 29, there is usedbelt-shaped metallic piece, etc. consisting of conductive metal, e.g.,aluminum, etc.

At the cathode 24, as active cathode material contained in the cathodecompounding agent layer 28, there is used material capable ofdoping/undoping lithium ion. In concrete terms, there may be used, e.g.,lithium transition metal compound oxide indicated by chemical expressionLi_(x) MO₂ (valence x of Li is within the range from 0.5 to 1.1, and Mis any kind one or plural kinds of compounds among transition metals),etc., metal sulphide or metal oxide which does not contain lithium suchas TiS₂, MoS₂, NbSe₂, V₂O₅, etc., or specific polymer, etc. Among thesematerials, as lithium transition metal compound oxide, there arementioned, e.g., lithium-cobalt compound oxide (LiCoO₂), lithium-nickelcompound oxide (LiNiO₂), Li_(x)Ni_(y)CO_(1-y)O₂ (valence x of lithiumand valence y of nickel vary depending upon charge/discharge state ofthe battery, and 1−y is valence of cobalt and these valences arerespectively ordinarily expressed as o<x<1, 0.7<y<1.02), and/or spineltype lithium manganese compound oxide expressed as LiMn₂O₄, etc.Further, at the cathode 2, as active cathode material, there may be usedany one kind of metal sulfide, metal oxide and lithium compound oxide,etc. which have been described above, or mixture in which pluralmaterials thereof are mixed.

At the cathode 24, as binding agent of the cathode compounding agentlayer 28, carbonaceous material, etc. may be added, or well knownadditive agent, etc. may be added as conductive material into the anodecompounding agent layer 28 in addition to the fact that there may beused resin material, etc., e.g., polyvinyl fluoride, polyvinylidenefluoride, polytetrafluoroethylene, etc. which are used as cathodecompounding agent of non-aqueous electrolyte battery. In addition, atthe cathode 24, foil-shaped metal or mesh-shaped metal, etc. consistingof conductive metal, e.g., aluminum, etc. may be used as the cathodecollector 27.

The anode 25 is caused to be of the structure in which anode compoundingagent liquid containing active anode material and binding agent iscoated, dried and pressurized with respect to the principal surface ofan anode collector 30 so that an anode compounding agent layer 31 iscompressed and formed on an anode collector 30. At the anode 25, ananode terminal 32 is connected to a predetermined position of the anodecollector 30. As the anode terminal 32, there may be used belt-shapedmetallic piece, etc. consisting of conductive metal, e.g., copper ornickel, etc.

At the anode 25, as active anode material contained (included) in theanode compounding agent layer 31, there may be used lithium, lithiumalloy or carbonaceous material capable of doping/undoping lithium ion,etc. As carbonaceous material capable of doping/undoping lithium ion,there may be used, e.g., low crystallinity (crystallinecharacteristic)carbon material obtained by sintering at a relatively lowtemperature less than 2000° C., and/or high crystallinity carbonmaterial, etc. such as artificial graphite obtained by firing (baking)material apt to be crystallized at a high temperature in the vicinity of3000° C. In concrete terms, there may be used thermal decompositioncarbon or the like, cokes or the like, graphite or the like,glass-shaped carbon fiber, organic high molecular compound fired (baked)body, carbon fiber and/or carbonaceous material such as activatedcarbon, etc. As the cokes or the like, there are, e.g., pitch cokes,needle cokes and/or petroleum cokes, etc. In this case, the organic highmolecular compound fired (baked) body is material obtained by firing(baking) phenol resin or furan resin, etc. at a suitable temperature tocarbonize such resin. These carbonaceous materials makes it possible tosuppress that lithium is precipitated toward the anode 25 side incharging/discharging the battery 2.

In addition to the above-described carbonaceous material, as activeanode material, there are mentioned, e.g., metal, alloy and elementwhich can compound with lithium, and compounds thereof, etc. As activeanode material, when, e.g., element which can compound with lithium isexpressed as M, there are compounds expressed by the chemical expressionof M_(x)M′_(y)Li_(z) (M′ is metal element except for Li element and Melement, valence x of M is numeric value larger than zero (0), andvalence y and valence z of Li of M′ are numeric value equal to 0 (zero)or more). In this chemical expression, e.g., B, Si, As, etc. which aresemiconductor element are mentioned as metal element. In concrete terms,there are mentioned, e.g., elements such as Mg, B, Al Ga, In, Si, Ge, SnPb, Sb, Bi, Cd, Ag, Zn, Hf, Zr, Y, B, Si, As, etc. and compoundscontaining these elements, Li—Al, Li—Al-M (M is either one or pluralkinds of transition metal elements of 2A group, 3B group and 4B group),AlSb, and CuMgSb, etc.

Particularly, as element which can compound with lithium, it ispreferable to use 3B typical elements. Among these elements, it ispreferable to use Si or Sn. Further, it is preferable to use Si. Inconcrete terms, as Si compound and Sn compound indicated by the chemicalexpression M_(x)Si, M_(x)Sn (M is one kind of elements or more exceptfor Si, Sn, and valence x of M is numeric value of 0 (zero) or more),there are mentioned, e.g., SiB₄, SiB₆, Mg₂Si, Mg₂Sn, Ni₂Si, TiSi₂,MoSi₂, NiSi₂, CaSi₂, CrSi₂, Cu₅Si, FeSi₂, MnSi₂, NbSi₂, TaSi₂, VSi₂,WSi₂, and ZnSi₂, etc. One kind of these compounds, or mixture obtainedby mixing plural kinds of compounds may be used.

Further, as active anode material, element compounds of 4B group exceptfor carbon containing one non-metal element or more may be alsoutilized. In such compound, plural kinds of elements of 4B group may becontained (included). In concrete terms, there are mentioned, e.g., SiC,Si₃N₄, Si₂N₂O, Ge₂N₂O, SiO_(x) (valence x of oxygen is within the rangeof 0<x≦2), SnO_(x) (valence x of oxygen is within the range of 0<x≦2),LiSiO, and LiSnO, etc. Any one kind of these compounds, or mixtureobtained by mixing plural kinds thereof may be used.

At the anode 25, as binding agent of the anode compounding agent layer31, there may be used resin material, etc., e.g., polyvinylidenefluoride or polytetrafluoroetylene, etc. used as anode compounding agentof the non-aqueous electrolyte battery. At the anode 25, as the anodecollector 30, there may be used, e.g., foil-shaped metal or mesh-shapedmetal, etc. consisting of conductive metal, etc. such as copper, etc.

A separator 26 serves to separate the cathode 24 and the anode 25. Theremay be used well known material ordinarily used as insulating microporous film of the non-aqueous electrolyte battery of this kind. Inconcrete terms, there may be used high molecular film, e.g.,polypropylene or polyethylene, etc. In addition, from the relationshipbetween lithium ionic conductivity and energy density, it is preferablethat the thickness of the separator 26 is as thin as possible. Theseparator 26 of which thickness is caused to be 30 μm or less is used.

The battery element 20 of such a configuration is a winding body inwhich the cathode 24 and the anode 25 are laminated through theseparator 26 and are wound in a length direction, and is caused to be ofthe structure in which a cathode terminal 29 is extended (projected)from one end surface of the winding axial direction, and an anodeterminal 32 is extended (projected) from the other end surface thereof.

The electrolytic solution 21 is a non-aqueous electrolytic solution inwhich electrolytic salt is dissolved into, e.g., non-aqueous solvent. Inthe electrolytic solution 21, as non-aqueous solvent, there may be used,e.g., ring-shaped carbonic ester compound, and/or cyclic carbonic estercompound or chain carbonic ester compound, etc. in which halogen radicalor acrylic halide radical is substituted for hydrogen. In concreteterms, there are mentioned propylene carbonate, ethylene carbonate,diethyl carbonate, dimethyl carbonate, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, γ-butyrolactone, tetrahydrofuran,2-methyltetrahydrofuran, 1, 3-dioxolan, 4 methy 1, 3 dioxolan, diethylether, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole,acetic ester, butyric ester, and propionic acid ester, etc. One kind ofthese compounds may be used thereamong. Particularly, from a viewpointof voltage stability, it is preferable to use, as non-aqueous solvent,propylene carbonate, dimethy carbonate and/or diethyl carbonate.

Moreover, as electrolytic salt, there are mentioned, e.g., LiPF₆,LiClO₄, LiAsF₆, LiBF₄, LiB(C₆H₅)₄, LiCH₃SO₃, LiCF₃SO₃, LiCl, and LiBr,etc. Any one kind of these materials or more may be used.

The armored can 22 is a cylindrical vessel having bottom portionconsisting of conductive metal, etc., e.g., iron, aluminum or stainlesssteel, etc., wherein a can bottom portion 22 a has shape such as circle.As the armored can 22, there may be used a cylindrical vessel havingbottom portion, which includes the can bottom portion 22 a having, e.g.,rectangular shape or oblate shape, etc.

The battery element 20 in which insulators 33 for preventing internalshort are disposed at both end surfaces is inserted into the armored can22, and an anode terminal 32 projected from the other end surface of thebattery element 20 is electrically connected to the can bottom portion22 a by soldering, etc. so that the armored can 22 is caused to serve asexternal anode terminal of the battery 2. In this example, in thebattery 2, the welding portion 3 a of the lead terminal 3 is welded tothe can bottom portion 22 a of the armored can 22 serving as one endsurface by the resistance-welding method.

At the armored can 22, a bead portion 22 b constricted toward the insideover the inner diameter entire circumference is provided in the vicinityof the opening portion thereof. When the cover body 23 is press-fittedinto the opening portion of the armored can 22 through gasket 34 toclose the cover, the bead portion 22 b is caused to serve as pedestal ofthe cover body 23 to determine the position where the cover body 23 isdisposed at the opening portion of the armored can 22, and to preventthe battery element 20 accommodated within the armored can 22 fromjumping out therefrom.

The armored can 22 is adapted so that the portion in the vicinity ofupper edge portion relative to the bead portion 22 b is caused toundergo bending processing, so-called caulking processing in the statewhere the battery element 20 is accommodated so that the cover body 23is press-fitted into the opening portion through the gasket 34, wherebythe cover body 23 is firmly fixed to the opening portion to hermeticallyseal the battery element 20 thereinto. Moreover, at the armored can 22,when caulking processing is implemented, the gasket 34 is protruded orprojected at the entire circumference of the edge portion of the openingportion so that the edge portion and the cover body 23 are not caused tobe in contact with each other.

The cover body 23 is press-fitted into the opening portion of thearmored can 22 in the state where a current interruption mechanismportion 35 for interrupting current flowing in the battery 2 whenbattery internal pressure of the battery 2 becomes equal to apredetermined pressure or more, a PTC (Positive Temperature Coefficient)element 36 for increasing electric resistance when current of apredetermined temperature or more, or a predetermined current value ormore flows in the battery 2 to lessen current flowing in the battery 2,and a terminal plate 37 serving as external cathode terminal of thebattery 2 are laminated in succession, and are accommodated within thegasket 34.

The current interruption mechanism portion 35 is composed of a safetyvalve 38 which is broken in the case where the battery internal pressurerises up to a predetermined value or more to escape air, etc. within thebattery toward the outside of the battery, a connecting plate 39 towhich the cathode terminal 29 is connected, a disc 40 to which theconnecting plate 39 is connected, and a disc holder 41 for insulatingthe safety valve 38 and the disc 40.

The safety valve 38 consists of conductive metal, etc., e.g., aluminum,etc., wherein press processing, etc. is implemented to the disc-shapedmetal plate so that there are formed a dish portion 38 a projectedtoward the battery element 20 side accommodated within the armored can22 and a projection portion 38 b projected from substantially the centerof the dish portion 38 a toward the battery element 20 side. Moreover,at the safety valve 38, a thin thickness portion 38 c which is brokenwhen the battery internal pressure becomes equal to a predeterminedvalue or more is provided at the dish portion 38 a.

The connecting plate 39 consists of conductive metal, etc., e.g.,aluminum, etc., wherein the projection portion 38 b of the safety valve38 is welded to one principal surface thereof and cathode terminal 29from which the battery element 20 is projected is welded to the otherprincipal surface by ultra-sonic welding, etc. so that the connectingplate 39 is connected.

The disc 40 consists of metal plate, etc. having, e.g., such a certainrigidity to have ability to plane characteristic, and is providedsubstantially at the central portion thereof with a hole portion 40 ainto which projection portion 38 b of the safety valve 38 is inserted.

The disc holder 41 consists of, e.g., insulating resin material, etc.,and exhibits annular shape so that the dish portion 38 a of the safetyvalve 38 and the disc 40 are fitted with respect to the innercircumferential side to thereby hold the dish portion 38 a and the disc40. Moreover, at the disc holder 41, a separation portion 41 a forseparating the dish portion 38 a of the safety valve 38 and the disc 40which have been fitted so that they are not in contact with each otheris provided in a manner to project toward the inside over the entireinner circumference. Further, at the disc holder 41, a hole portion 41 binto which the projection portion 38 b of the safety valve 38 isinserted is provided substantially at the central portion of theseparation portion 41 a.

Further, the current interruption mechanism portion 35 is caused to beof the configuration in which the dish portion 38 a of the safety valve38 and the disc 40 are fitted with respect to the inner circumferentialside of the disc holder 41 so that they are not caused to be in contactwith each other by the separation portion 41 a, and the projectionportion 38 b of the safety valve 38 is inserted into a hole portion 41 bof the disc holder 41 and a hole portion 40 a of the disc 40 so that itis welded to the connecting plate 39 by, e.g., resistance welding methodor ultra-sonic welding method, etc. Namely, the current interruptionmechanism portion 35 is adapted so that the connecting plate 39, thedisc 40, the disc holder 41 and the safety valve 38 are laminated insuccession, and the projection portion of the safety valve 38 isconnected to the connecting plate 39 in a manner to penetrate the discholder 41 and the disc 40.

At the current interruption mechanism portion 35 of such aconfiguration, in accordance with elevation of the battery internalpressure, the dish portion 38 a of the safety valve 38 is deformed in amanner to swell toward the outside opposite to the battery element 20side. Further, since the disc 40 suppresses that the currentinterruption mechanism portion 35 attempts to move toward the outside ofthe connecting plate 39 connected to the projection portion 38 bfollowed by deformation of the dish portion 38 a of the safety valve 38,connection between the projection portion 38 b of the safety valve 38and the connecting plate 39 is interrupted. In a manner as stated above,at the current interruption mechanism portion 35, when battery internalpressure rises, connection between the battery element 20 and the coverbody 23 is interrupted to suppress that a current flows no longer sothat battery internal pressure is further elevated.

When the battery temperatures rises to a predetermined value or more, orcurrent of a predetermined value or more is caused to flow so thattemperature rises, the PTC element 36 enlarges its electric resistanceto reduce current flowing in the battery 2. Thus, at the battery 2, thePTC element 36 controls current value, thus making it possible tosuppress temperature elevation of the battery inside. Moreover, when itselectric resistance becomes large so that current flowing in the battery2 becomes small and temperature is thus lowered, the electric resistanceof the PTC element 36 becomes small so that current is caused to flow inthe battery 2 for a second time.

The terminal plate 37 consists of conductive metal, etc. containing anyone kind of, e.g., iron, aluminum, stainless steel, nickel, zinc andzinc alloy, etc., or plural kinds thereof, and is electrically connectedto the cathode terminal 29 projected from the battery element 20 throughthe connecting plate 39, the safety value 38 and the PTC element 36 sothat the terminal plate 37 functions as cathode external terminal of thebattery 2.

In the terminal plate 37, e.g., press processing, etc. is implemented todisc-shaped metal plate so that a terminal portion 37 a projected towardthe side opposite to the battery element 20 accommodated within thearmored can 22 is provided. The terminal portion 37 a serves as aconnecting portion of the cathode side with respect to the external sideof the terminal plate 37 serving as the cathode external terminal, andconnection terminal from the external is connected thereto by, e.g.,contact and/welding, etc. In this example, in the battery 2, the weldingportion 3 a of the lead terminal 3 is welded to the terminal portion 37a of the terminal plate 37 serving as the other end surface by theresistance-welding method.

Moreover, at the terminal plate 37, there is provided gas escape hole,etc. (not shown) for escaping gas, etc. discharged toward the externalas the result of the fact that the safety valve 38 is broken by, e.g.,elevation of the battery internal pressure.

Then, a method of assembling the battery pack 1 in which the battery 2of the configuration as stated above is accommodated will be explained.First, a method of welding the lead terminals 3 to the battery 2 will beexplained. It is to be noted that explanation will be given here bytaking the example of the case where the lead terminal 3 is connected tothe welding portion 37 a of the cover body 23.

The lead terminals 3 are welded to both end surfaces serving as externalterminal of the battery 2 by a resistance-welding machine 50 shown inFIG. 10. The resistance-welding machine 50 includes a welding head 52provided with a pair of electrode rods 51 a, 51 b for allowing currentto flow with respect to welded material, a welding transformer unit 53for allowing current to flow in either of the electrode rods 51 a, 51 b,a control unit 54 for controlling currents, etc. flowing in theelectrode rods 51 a, 51 b, and a switch unit 55 for sending ON signalindicating start of welding operation to the control unit 54.

The welding head 52 comprises a clamping portion 56 driven in upper andlower directions by air cylinder, etc. through biasing member, etc. (notshown) such as coil spring, etc., a pair of electrode rod holdingportions 57 a, 57 b moved in a manner interlocking with drive of theclamping portion 56, and a mount table 58 adapted for mounting thebattery 2 serving as welded material thereon and formed by insulatingmaterial so that the battery 2 is not externally shorted. Further, inthe welding head 52, the electrode rods 51 a, 51 b are respectively heldby a pair of electrode rod holding portions 57 a, 57 b placed in thestate where they are insulated from each other. Moreover, the weldinghead 52 also includes limit switch (not shown) for transmitting ONsignal when a pair of electrode rods 51 a, 51 b are pressed by weldedmaterial at a predetermined pressure value.

The welding transformer unit 53 is connected to respective pair ofelectrode rod holding portions 57 a, 57 b of the welding head 52 througha pair of welding cables 59 a, 59 b taken out from welding transformer(not shown).

The control unit 54 comprises Central Processing Unit (hereinafterreferred to as CPU), etc., and serves to control the entirety of theresistance-welding machine 50 in accordance with electric signal such asON signal and/or instruction signal, etc. which have been transmittedfrom the external. The control unit 54 comprises a power supply switch54 a for controlling ON/OFF operation of the entirety of the apparatus,a mode changeover switch 54 b for performing switching, etc. of voltageapplied to the piar of electrode rods 51 a, 51 b and/or current flowingtherein, etc., and a monitor unit 54 c, etc. for displaying voltageapplied to the piar of electrode rods 51 a, 51 b and/or current flowingtherein, etc. Moreover, the control unit 54 also comprises an actuatorcable 60 connected to the welding head 52 and adapted for performingtransfer of electronic signal to and from the welding head 52, a powercable 61 connected to the welding transformer unit 53 and adapted forperforming transfer of electric signal to and from the weldingtransformer unit 52, and a voltage detection cable 62 connected torespective pair of electrode rod holding portions 57 a, 57 b to detectvoltage across electrode rods 51 a, 51 b, etc.

The switch unit 55 is so-called foot switch connected to the controlunit 54 by cable, and serving to send ON signal for starting weldingoperation to the control unit 54.

In connecting the lead terminal 3 to the terminal portion 37 a of thecover body 23 by using the resistance-welding machine 50 of such aconfiguration, the battery 2 is first mounted on a mount table 58 of thewelding head 52 in such a manner that the cover body 23 and theelectrode rods 51 a, 51 b are opposite to each other as shown in FIG.11.

Then, as shown in FIG. 12, the welding portion 3 a of the lead terminal3 is disposed at the terminal portion 37 a of the cover body 23 in sucha manner that the welding portion 3 a of the lead terminal 3 is oppositethereto. Thus, flat surface sides having no offset of the weldingportion 3 a are caused to come into contact therewith.

Then, the switch unit 55 of the resistance-welding machine 50 is turnedON to weld the lead terminal 3 to the terminal portion 37 a of the coverbody 23.

In concrete terms, when the switch unit 55 is turned ON, the controlunit 54 is supplied with ON signal through cable to send, to the weldinghead 52, an instruction signal that the CPU operates a clamping portion56 by this ON signal.

Then, the welding head 52 falls the clamping portion 56 by instructionsignal from the control unit 54 so that a pair of electrode rods 51 a,51 b respectively press welding portions 3 a of the lead terminals 3followed by this falling movement.

Then, at the welding head 52, when pressures that the pair of electroderods 51 a, 51 b respectively press welding portions 3 a of leadterminals 3 reach a predetermined value, limit switch includedtherewithin is turned ON to send ON signal.

Then, the control unit 54 is supplied with ON signal that the limitswitch of the welding head 52 has sent through the actuator cable 60 tosend, to the transformer unit 53, an instruction signal to the effectthat the CPU allows current of a predetermined value to flow in theelectrode rod 51 a by the ON signal.

Then, current that the welding transformer unit 53 has transmitted bythe instruction signal which has been sent from the control unit 54flows from the electrode rod 51 a through the welding cable 59 a and theelectrode rod holding portion 57 a to the terminal portion 37 a of theterminal plate 37 through the welding portion 3 a of the lead terminal3.

At this time, as shown in FIG. 13, electricity of predetermined currentvalue and predetermined voltage value is caused to flow from oneelectrode rod 51 a to the other electrode rod 51 b at the lead terminal3 so that current of the large part flows via a path of the weldingportion 3 a, the terminal portion 37 a and the welding portion 3 a,i.e., a path indicated by arrow A in FIG. 13 in practical sense.

Namely, at the lead terminal 3, the thickness of the welding portion 3 ais caused to be thinner than thickness of the conductive portion 3 c.Since distance B between the electrode rod 51 a and the terminal portion37 a is shortened, current for resistance-welding is permitted to flowin a thickness direction of the welding portion 3 a. Thus, it can besuppressed that current flowing in plane surface of the lead terminal asin the prior art, so-called reactive current takes place.

Thus, at the lead terminal 3, current for welding flows to much degreein thickness direction of the welding portion 3 a. As a result, electricresistance of the welding portion 3 a is increased, and colorific valueby the electric resistance is also increased. Further, at the leadterminal 3, quantity of metal to be thermally fused or molten at thewelding portion 3 a and the terminal portion 37 a is increased, andwelding block produced as the result of the welding portion 3 a and theterminal portion 37 a are welded each other by heat, so-called nugget 63can be enlarged. In concrete terms, heat quantity of the welding portion3 a here results in value proportional to square of current forresistance-welding, which flows by the electrode rod 51 a.

Accordingly, at the lead terminal 3, since the welding portion 3 a iswelded to the terminal portion 37 a by large welding nugget 63 with highwelding strength, the lead terminal 3 is connected to the terminalportion 37 a of the cover body 23 in the state where connectionreliability has been enhanced (improved).

At the lead terminal 3, as shown in FIG. 14, slits 3 d are providedbetween positions where a pair of electrode rods 51 a, 51 b are causedto be in contact therewith, thereby making it possible to weld thewelding portion 3 a to the terminal portion 37 in the state where theconnecting reliability has been further enhanced (improved). In concreteterms, as shown in FIG. 15, in addition to the fact that distancebetween the electrode rod 51 a and the terminal portion 37 can beshortened, reactive current flowing only through the lead terminal 3 inthe electrode rod 51 b from the electrode rod 51 a can be furtherreduced by the slits 3 d. Thus, further many active current is permittedto flow in thickness direction of the lead terminal 3. Accordingly, inthe lead terminal 3, the slits 3 d are provided so that welding nugget63 can be further enlarged. Thus, the lead terminal portion is welded tothe terminal portion 37 a with higher welding strength.

While explanation has been given in the above-described example bytaking the example of lead terminal 3 provided with welding portion 3 aformed to be substantially rectangular, the present invention is notlimited to such implementation, but the welding portion 3 a may be asdiamond shape, etc. in a manner corresponding to positions of the pairof electrode rods 51 a, 51 b caused to be in contact therewith as shownin FIG. 16, for example.

Further, lead terminals 3 may be welded to both end surfaces ofrespective pair of batteries 2 a, 2 b by a method as stated above tothereby have ability to make (manufacture) the battery module 6. In thisexample, in the battery 2, an insulating washer 42 and an insulatingtube 43 which are caused to intervene between lead terminals 3 connectedto the cover body 23 and the armored can 22 are attached so that thearmored can 22 and the cover body 23 are not caused to be in contactwith each other through lead terminals 3 to make external-short. Inconcrete terms, the insulating washer 42 is attached at the upperportion of the cover body 23 so that the insulating tube 43 at leastcovers the portion in the vicinity of the opening portion of the armoredcan 22 and the outer circumferential surface thereof.

Then, the connecting portion 3 b of the lead terminal 3 is welded toconnecting lands 7 provided at the circuit wiring board 4 by, e.g.,resistance-welding, ultrasonic welding, laser welding, plasma welding orsoldering, etc. so that the battery module 6 manufactured in a manner asstated above is electrically connected to the circuit wiring board 4.

Further, as shown in FIG. 5, the battery module 6 and the circuit wiringboard 4 are accommodated between the upper case 10 and the lower case 11of the accommodating case 5 thereafter to connect or bond these upperand lower cases 10 and 11 in such a manner to but the peripheral wallsthereof with each other. In a manner as stated above, the battery pack 1in which the connector 9 is exposed from the opening portion as shown inFIG. 4 is assembled.

In the battery pack 1 assembled in a manner as stated above, leadterminals 3 are welded to both end surfaces of the pair of batteries 2a, 2 b at the battery module in the state where the connectingreliability has been enhanced (improved). When impact is applied fromthe external, e.g., the battery pack 1 is erroneously fallen down, etc.in detaching it from electronic equipment, etc. as in the prior art, itis possible to prevent inconvenience such that connection between thebattery and the lead terminals is broken at the welding portion so thatthe battery pack is placed in unusable state.

In this battery pack 1, the conductive portion 3 c of the lead terminal3 is caused to be thicker than the welding portion 3 a. Thus, it ispossible to lessen electric resistance of the lead terminal 3 producedby, e.g., current flowing in length direction of the lead terminal 3 inperforming charge/discharge operation.

Thus, in the battery pack 1, since electric resistance of the leadterminal 3 is caused to be small, it is possible to suppress calorificvalue of lead terminal 3 by electric resistance when current forcharge/discharge operation flows in the lead terminal 3. Accordingly, inthe battery pack 1, it can be prevented that characteristic isdeteriorated by heat of the lead terminal heated by current incharge/discharge operation as in the case of the prior art.

In the battery pack 1, since electric resistance of the lead terminal 3is caused to be small, it is possible to prevent inconvenience such thattemperature fuse or thermostat, etc. provided within the pack becomesoperative by electric resistance of the lead terminal when large currentis caused to flow as in the case of the prior art, and it thus becomesimpossible to perform charge/discharge operation. Accordingly, in thebattery pack 1, it is possible to perform so-called charge/dischargeoperation by the large current in which, e.g., current of the order of 1C to 2 C per battery based on requirement of electronic equipment, etc.is caused to flow.

Further, in the battery pack 1, since the conductive portion 3 c iscaused to be thicker than the welding portion 3 a so that the surfacearea of the lead terminal 3 is large, the lead terminal 3 functions asradiating plate, thereby making it possible to further suppress heat ofthe lead terminal 3 by electric resistance when current forcharge/discharge operation flows.

While explanation has been given in the above-described example bytaking the example of the lead terminal where only thickness of thewelding portion 3 a has been thinned, the present invention is notlimited to such implementation, but can be also applied to lead terminalhaving bent portion 70 a in which the thickness thereof is caused to bethinner than the thickness of the conductive portion 3 c as in the caseof the lead terminal 70 shown in FIGS. 17 and 18. It is to be notedthat, in lead terminals 70, 71, 72, 73, 74 which will be explainedbelow, explanation will be omitted and the same reference numeral areused in connection with materials, shapes and portions which are similarto those of the above-described lead terminal 3.

The lead terminal 70 is provided with a bent portion 70 a of whichthickness has been thinned with respect to the thickness of theconductive portion 3 c over the opposite other edge end from one edgeend in a short direction at the conductive portion 3 c toward oppositeother edge end, and can be easily bent in a length direction with thebent portion 70 a being as reference.

At the lead terminal 70, the bent portion 70 a is formed as the resultof the fact that etching processing, etc. is implemented theretosimilarly to the welding portion 3 a. Accordingly, in forming thewelding portion 3 a, the bent portion 70 a can be collectively formed.The bent portion 70 a is adapted so that, in order to facilitate bendingof the lead terminal 70, offset obtained by engraving the principalsurface of the conductive portion 3 c is disposed in a manner facedtoward the outside when the lead terminal 70 is bent.

Moreover, in the above-described example, in addition to the leadterminal 3 and/or the lead terminal 70, there may be also used a leadterminal in which, e.g., the thickness of the connecting portion 71 aconnected to the connecting land 7 of the circuit wiring board 4 iscaused to be thinner than thickness of the conductive portion 3 c as inthe case of the lead terminal 71 shown in FIG. 19.

At the lead terminal 71, since there is provided connecting portion 71 aof which thickness is caused to be thinner than the thickness of theconductive portion 3 c, it can be suppressed that heat used forsoldering is radiated from the connecting portion 71 a in soldering theconductive portion 71 a to connecting land 7 of the circuit wiring board4. Accordingly, the lead terminal 71 can be connected to the connectingland 7 in the state where the connection reliability of the connectingportion 71 a has been enhanced (improved). Moreover, since theconnecting portion 71 a can be easily warmed, it is possible to shortenthe time required for soldering the connecting portion 71 a to theconnecting land 7. In this example, also in the lead terminal 71, theconnecting portion 71 a is thinned as the result of the fact thatetching processing, etc. is implemented thereto similarly to the weldingportion 3 a. Accordingly, connecting portions 71 a can be collectivelyformed in forming the welding portions 3 a.

Further, in the above-described example, there may be also used leadterminal in which plural connecting portions 72 a of which thickness iscaused to be thinner than the thickness of the conductive portion 3 care provided, e.g., only at portions with which a pair of electrode rods51 a, 51 b are caused to be in contact in resistance-welding.

At the lead terminal 72, since the area of the conductive portion 3 c ofwhich thickness is thicker than the welding portion 72 a becomes large,it is possible to further reduce electric resistance produced by currentflowing in a length direction, e.g., in performing charge/dischargeoperation. Accordingly, at the lead terminal 72, since the electricresistance is caused to be smaller, heat and voltage drop by electricresistance produced by current for charge/discharge operation can befurther suppressed.

Furthermore, in the above-described example, as in the case of the leadterminal 73 shown in FIG. 21, there may also used, e.g., a lead terminalin which hole portions 73 b penetrated in a thickness direction areformed at the welding portion 73 a.

At this lead terminal 73, since hole portions 73 b are provided at thewelding portion 73 a, yielding at the time of manufacturing pack can beimproved such that hole portion 73 b is caused to be mark in performingresistance-welding so that the time required for resistance-welding canbe shortened, etc.

Furthermore, while explanation has been given in the above-describedexample by taking the example of lead terminal 3 in which the weldingportion 3 a, the connecting portion 3 b and the conductive portion 3 care integrally formed by single conductive metal, etc., the presentinvention is not limited to such implementation, but there can be alsoused lead terminal formed by clad material, etc. in which, e.g., plurallayers of conductive metals having different conductivities arelaminated as in the case of the lead terminal 74 shown in FIGS. 22A to22B.

The lead terminal 74 is constituted by, e.g., a first metal layer 74 aconsisting of first conductive metal containing any one kind or more ofnickel, nickel alloy, iron, iron alloy, stainless steel, zinc and zincalloy, and a second conductive metal layer 74 b consisting of secondconductive metal containing any one kind or more of copper, copperalloy, silver, silver alloy, gold, gold alloy, platinum, platinum alloy,aluminum, aluminum alloy, tungsten, tungsten alloy, beryllium, berylliumalloy, rhodium, and rhodium alloy. In concrete terms, the lead terminal74 is laminated material, i.e., clad material in which metal foilconsisting of first conductive metal and metal foil consisting of secondconductive metal having conductivity caused to be higher than that ofthe first conductivity metal are pressurized while heating theseconductive metals in the state where they are laminated so that oppositeprincipal surfaces of these metal foils are press-fitted and areconnected (bonded) to constitute the first metal layer 74 a and thesecond metal layer 74 b.

It is to be noted that, in the lead terminal 74, e.g., metal foilconsisting of first conductive metal and metal foil consisting of secondconductive metal may be also heated and pressurized, etc. in the statewhere those metal foils are laminated through, e.g., conductive adhesiveagent or soldering film, etc. therebetween to laminate and connect(bond) the first metal layer 74 a and the second metal layer 74 b.Moreover, the first metal layer 74 a and the second metal layer 74 b maybe laminated and connected (bonded) by the cold pressure-fit method,etc. of simply pressurizing the first metal layer 74 a and the secondmetal layer 74 b in the state where they are laminated. Further, thefirst metal layer 74 a and the second metal layer 74 b may beresistance-welded at a predetermined portion in the state where they arelaminated to thereby laminate and connect (bond) them.

Further, etching processing, etc. is implemented in the state whereportions except for the portion where welding portion 74 c is providedof the principal surface of the second metal layer 74 b is masked untilthe first metal layer 74 a is exposed so that welding portion 74 wherethe first conductive metal is exposed is formed. In this example,similarly to the above-described lead terminal 3, the lead terminal 74also includes a connecting portion 74 d connected to connection land 7of the circuit wiring board 4 by soldering, etc., and a conductiveportion 74 e for allowing the welding portion 74 c and the connectingportion 74 d to electrically conduct.

At the lead terminal 74, the welding portion 74 c is constituted only byfirst conductivity metal having conductivity lower than that of thesecond conductive metal, and electric resistance per unit volume byactive current flowing in thickness direction of the welding portion 74c in resistance-welding becomes large. From this fact, calorific valueby this electric resistance becomes large.

In concrete terms, at the lead terminal 74, since thermal conductivityof the first conductive metal having low conductivity is generally low,heat of the welding portion 74 c is difficult to be radiated toward theperiphery so that temperature elevation of the welding portion 74 cbecomes large. Moreover, at the lead terminal 74 c, the welding portion74 c is thin. For example, since distance between the electrode rod 51 aand the terminal portion 37 a in performing resistance-welding becomesshort, value of current for resistance-welding flowing in the weldingportion 74 c is increased. From these facts, at the lead terminal 74,the welding portion 74 c can be welded to the external terminal of thebattery 2 with high welding strength. In this case, half part or more ofcalorific value contributing to the resistance-welding here is contactresistance of the connecting (bonding) surface between the weldingportion 74 c and the external terminal of the battery 2.

At the lead terminal 74, a conductive portion 74 e is adapted so thatsecond metal layers 74 b formed by metal such as copper, etc. havingconductivity higher than that of the first metal layer 74 a is laminatedin addition to the first metal layer 74 a. From this fact, as comparedto the lead terminal 3 formed by one kind of metal or alloy, e.g.,nickel, iron, stainless steel, zinc, and zinc alloy, etc., electricresistance produced by current flowing in a length direction, e.g., inperforming charge/discharge operation of the battery pack 1 can befurther reduced. Accordingly, at the lead terminal 74, since electricresistance can be further reduced by the second metal layer 74 b of theconductive portion 74 e, it is possible to further suppress calorificvalue and voltage drop by electric resistance produced by current forcharge/discharge operation.

At the lead terminal 74, it is also possible to provide a bent portion70 a as in the case of the above-described lead terminal 70, and it isalso possible to thin the connecting portion 74 d so that it is thinnerthan the conductive portion 74 e as in the case of the above-describedlead terminal 71. Moreover, at the lead terminal 74, while explanationhas been given by taking the example of the case where clad member oftwo-layer structure is used, clad material, etc. of two layers or moremay be also used.

At the lead terminal 74, the surface of conductive metal, etc. havingrust proof characteristic, e.g., gold or nickel, etc. is covered byelectrolytic plating or non-electrolytic plating, etc., thereby alsomaking it possible to prevent rust. Thus, at the lead terminal 74, sincethe surface thereof is caused to undergo rust-proofing so that largecurrent flows in the welding portion 74 c at the time ofresistance-welding. From this fact, it is possible to reasonablydissolve the welding portion 74 c and the external terminal of thebattery. Thus, welding strength can be increased.

For example, in the case where rust takes place on the surface of thelead terminal 74, there is the possibility that current in performingresistance-welding become difficult to flow in the welding portion 74 con the connecting surface by rust so that it becomes difficult toperform resistance-welding. Moreover, in this case, at the connectingportion 74 d, since rust prevents alloy layer formation with respect tosolder in performing soldering with respect to connecting land 7, thereis the possibility that connecting strength with respect to theconnecting land 7 may be weakened. Particularly, at the lead terminal74, in the case where, e.g., copper is included, because rust is easy totake place, effect/advantage resulting from the fact that the surface iscovered by conductive metal having rust-proof characteristic as statedabove becomes great.

It is to be noted that in the case where the surface of the leadterminal 74 is covered by conductive metal having high rust proofcharacteristic, since the layer of conductive metal having rust proofcharacteristic is formed by plating, etc. so that it is thin, and theconductive metal having high rust characteristic is melt into the leadterminal 74 side at the time of resistance-welding, it is possible toperform resistance-welding of the welding portion 74 c and the externalterminal of the battery without lowering welding strength. Moreover,while explanation has been given here by taking the example of the leadterminal 74 consisting of clad material, etc., similareffects/advantages can be obtained also in the case where the layer ofconductive metal having high rust characteristic is provided on thesurface of the lead terminal 3, etc. consisting of the above-describedone kind of metal or alloy, etc.

Furthermore, while explanation has been given in the above-describedexample by taking the example of the battery pack 1 provided with singlebattery module 6 in which batteries 2 a, 2 b are connected in parallel,the present invention is not limited to the battery pack 1 of such aconfiguration, but can be also applied to battery pack 80 provided withtwo battery modules or more in which two batteries or more are providedas shown in FIG. 23.

Similarly to the above-described battery pack 1, the battery pack 80 isloaded with respect to loading portion provided at electronic equipment,etc., e.g., note-type personal computer, etc. to have ability to stablysupply power of a predetermined voltage with respect to electronicequipment, etc.

Further, the battery pack 80 includes substantially columnar sixbatteries 81 a, 81 b, 81 c, 81 d, 81 e, 81 f serving as power generatingelement, lead terminals 82 a, 82 b connected to external terminals ofthese batteries 81 a to 81 f, and a circuit wiring board 83 electricallyconnected to the batteries 81 a to 81 f and serving to performcharge/discharge control, etc. with respect to the batteries 81 a to 81f, wherein the batteries 81 a to 81 f, the lead terminal 82 and thecircuit wiring board 83 are accommodated within substantially box-shapedaccommodating case 84.

The battery pack 80 is adapted so that batteries 81 a to 81 f areconnected in parallel three by three to respectively constituteintegrated battery modules 85 a, 85 b, and these battery modules 85 a,85 b are accommodated in the state where they are connected in parallelon the circuit wiring board 83. In concrete terms, the battery module 85a is constituted by batteries 81 a to 81 c, and the battery module 85 bis constituted by batteries 81 d to 81 f. It is to be noted that whileexplanation will be given here in connection with battery modules 85 a,85 b in which batteries 81 a to 81 f are connected in parallel three bythree, the present invention is not limited to such implementation, but,e.g., battery module in which plural batteries 81 a to 81 f areconnected in series may be employed, and the number of battery modulesand/or arrangement thereof may be arbitrarily selected. In this example,in the case where unspecific batteries 81 a to 81 f are indicated, labelis made simply as battery 81.

In the battery pack 80, in order to connect batteries 81 a to 81 f inparallel three by three to constitute battery modules 85 a, 85 b, leadterminals 82 a, 82 b consisting of conductive metal, etc. which arematerial similar to the above-described lead terminal 3. In concreteterms, the lead terminal 82 a connects end surfaces caused to have thesame polarity of the batteries 81 a to 81 c at the battery module 85 aand end surfaces caused to have opposite polarity with respect to theend surface connected at the lead terminal 82 a of the battery module 85a of batteries 81 d to 84 f at the battery module 85 b, and the leadterminal 82 b collectively connects end surface opposite to the sidewith respect to the end surface connected at the lead terminal 82 a ofthe battery modules 85 a, 85 b. Namely, the lead terminal 82 b serves toconnect, in series, the battery module 85 a in which batteries 81 a to81 c are connected in parallel and the battery module 85 b in whichbatteries 81 d to 81 f are connected in parallel.

The lead terminals 82 a, 82 b caused to constitute the battery modules85 a, 85 b are belt-shaped conductive metal consisting of materialsimilar to that of the above-described lead terminal 3, and includesplural welding portions 86 connected to both end surfaces serving asexternal terminal of the battery 82, a connecting portion 87 connectedto a connection land 91, etc. of the circuit wiring board 83, and aconductive portion 88 positioned between these welding portions 86 andbetween the welding portion 86 and the connecting portion 87, andserving to allow connection portions to electrically conduct. Moreover,in the lead terminal 82 b, in addition to these welding portion 86,connecting portion 87 and conductive portion 88, a bent portion 89similar to the above-described lead terminal 70 is provided in thevicinity of substantially central portion in length direction.

In these lead terminals 82 a, 82 b, similarly to the lead terminal 3,thickness of the welding portion 86 is caused to be within the rangethinner than thickness of the conductive portion 88. For this reason,since welding portions 86 respectively welded to both end surfacesserving as external terminal of the battery 81 are thinner than theconductive portion 88 in the lead terminals 82 a, 82 b, large part ofcurrent for welding flowing in the welding portion 86 in welding endsurface of the battery 81 and the welding portion 86 is permitted toflow in thickness direction of the welding portion 86. Accordingly, evenat the lead terminals 82 a, 82 b, similarly to the above-described leadterminal 3, the welding portion 86 can be welded to the end surface ofthe battery 81 with high welding strength.

Moreover, at these lead terminals 82 a, 82 b, since the conductiveportion 88 for allowing the welding portion 86 welded to the battery 81and the connecting portion 87 connected to the circuit wiring board 83to electrically conduct is thicker than the welding portion 86, electricresistance of the conductive portion 88 in allowing electricity(current) for charging/discharging the battery 81 to flow can bereduced. Accordingly, even at these lead terminals 82 a, 82 b, even inthe case where large current of the order of 1 C to 2 C flows in thebattery 81, e.g., by requirement of electronic equipment, etc.,similarly to the above-described lead terminal 3 calorific value byelectric resistance can be reduced.

Further, at the lead terminal 82 b, since bent portion 89 similar to theabove-described lead terminal 70 is provided, it is possible to easilyperform bending of the lead terminal 82 b in a length direction with thebent portion 89 being as reference.

In this example, also in lead terminals 82 a, 82 b, etching processing,etc. is implemented in the state where portions except for the portionswhere the welding portion 86 and/or bent portion 89 are provided aremasked so that the welding portions 86 and/or the bent portion 89 whichhave thin thickness are provided to control the time where those leadterminals are immersed into etchant, etc., thereby permitting theseportions to have a predetermined thickness. Moreover, these weldingportion 86 and/or bending portion 89 can be formed as lead terminals 82a, 82 b by a method, e.g., laser processing or drawing processing, etc.in addition to etching processing, etc.

In addition to effects/advantages as stated above, since these leadterminals 82 a, 82 b connect both end surfaces of plural batteries 81,the battery 81 is prevented from being rotated in outer circumferentialdirection to fix these batteries 81 in the state where they are adjacentto each other.

Further, as the result of the fact that the connecting portion 87 isdirectly welded to connecting land 91, etc. of the circuit wiring board83 by, e.g., soldering, etc., the lead terminals 82 a, 82 b electricallyconnect the circuit wiring board 83 and the battery modules 85 a, 85 bare electrically connected. Moreover, at the lead terminals 82 a, 82 b,the connecting portion 87 is bent at the boundary portion with respectto the conductive portion 89 so that it is caused to be along the outercircumferential surface of the battery 81 to also have ability toconnect battery modules 85 a, 85 b to the circuit wiring board 83through lead wire 90 and/or temperature fuse element 97, etc. which areconnected to the connecting portion 87 by implementing soldering, etc.thereto.

In this example, in the case where the connecting portion 87 is bent atthe boundary portion with respect to the conductive portion 89 in amanner along the outer circumferential surface of the battery 81, theconnecting portion 87 is caused to be along space formed between outercircumferential surfaces of the batteries 81 adjacent to each other.Namely, space formed as the result of the fact that outercircumferential surfaces of respectively substantially columnarbatteries 81 are caused to be adjacent results in dead space within theaccommodating case 4. The connecting portion 87 for lead terminals 82 a,82 b is disposed at the dead space. Thus, in the battery modules 85 a,85 b, the connecting portions 87 are not put between adjacent batteries81 so that they can be integrated in the state where no gap is formedbetween adjacent batteries 81. Thus, miniaturization can be realized. Inthe battery module 85 a, the connecting portions 87 for lead terminals82 a, 82 b are disposed at the dead space formed between the adjacentbatteries 81 a and 81 b, and in the battery module 85 b, the connectingportions 87 for lead terminals 82 a, 82 b are disposed at the dead spaceformed between the adjacent batteries 81 e and 81 f.

The circuit wiring board 83 to which battery modules 85 a, 85 b areconnected through lead terminal 82 a and/or lead wire 90 is adapted sothat pattern wiring (not shown) consisting of conductive metal, etc. andincluding lead terminal 82 a and/or connecting land 91 to which the leadwire 90 is connected, and/or electronic circuit, etc. (not shown)connected to the pattern wiring and serving to perform charge/dischargecontrol, and/or over-discharge and/or over-charge protection, etc. isprovided on a plate-shaped base portion 92 consisting of insulatingresin, etc.

Moreover, an external unit 93 electrically connected to pattern wiring,etc. by, e.g., soldering, etc. is attached to the circuit wiring board83. When the battery pack 80 is connected to the electronic equipment,the external terminal 93 is engaged with external terminal, etc.provided at the electronic equipment so that the external terminal 93 iselectrically connected thereto to thereby function as a supply port forsupplying electricity (current) with respect to electronic equipments,etc. Further, in charging the battery modules 85 a, 85 b, the externalterminal 93 serves as a connecting portion to which, e.g., AC powersupply, etc. is connected. The circuit wiring board 83 is accommodatedwithin an accommodating case 84 in a manner along the side wall of theaccommodating case 84 in the state where, e.g., side wall ofsubstantially box-shaped accommodating case 84 and the principal surfaceof the base portion 82 are opposite to each other.

The accommodating case 84 within which battery modules 85 a, 85 b andcircuit wiring board 83 are accommodated consists of insulating resin,etc., e.g., polycarbonate or ABS resin, etc., and is composed of anupper case 94 and a lower case 95. The upper case 94 and the lower case95 respectively have shape in which side walls are projected along theouter circumferential edge portion of substantially rectangularprincipal surfaces and respective side walls are butted to each other sothat substantially box-shaped accommodating case 84 is provided.

At the accommodating case 84, an opening portion 95 a for allowing theexternal terminal 93 provided at the circuit wiring board 83 to beexposed to the outside is formed at the side wall of the lower case 95.

Further, within the battery pack 80 of such a configuration, there arealso accommodated, in addition to the battery modules 85 a, 85 b, thecircuit wiring board 83 and/or the lead wire 90 which have beendescribed above, etc., e.g., an insulator 96 a for insulation forpreventing contact between battery modules 85 a, 86 b and circuit wiringboard 83 and/or contact between battery modules 85 a, 85 b and the leadwire 90, a holding insulator 96 b for holding the lead wire 90 at deadspace provided at battery modules 85 a, 85 b, and a temperature fuseelement 97 for detecting temperature changes of the battery modules 85a, 85 b to interrupt current when temperature reaches a predeterminedvalue or more, etc.

The insulator 96 a for insulation consists of sheet-shaped insulatingmaterial, etc., e.g., polyethylene, polypropylene, or imcombusitiblepaper, etc., and is disposed between battery modules 85 a, 85 b and thelead wire 90, and/or between the battery modules 85 a, 85 b and thecircuit wiring board 83. Thus, at the battery pack 80, when itundergoes, e.g., impact of falling, etc., since the insulator 96 aserves to prevent battery modules 85 a, 85 b from coming into contactwith the circuit wiring board 83 and/or the lead wire 90, it is possibleto prevent external short of the battery 81 taking place as the resultof the fact that the battery modules 85 a, 85 b come into contact withthe circuit wiring board 83 and/or the lead wire 90.

The holding insulator 96 b consists of sheet-shaped insulating material,etc., e.g., polyethylene, polypropyrene, or imcombustible paper, etc.The holding insulator 96 b has shape in which sheet-shaped insulatingmaterial is valley-folded at the tangential line where outercircumferential surfaces of adjacent batteries 81 at the battery modules85 a, 85 b are in contact with each other. Further, at the holdinginsulator 96 b, lead wire 90 and/or temperature fuse element 97, etc.are disposed at portions of valley, thereby making it possible to holdthe lead wire 90 and/or temperature fuse element 97, etc. at dead spacewhere the battery modules 85 a, 85 b are provided.

Moreover, at the battery pack 80, when it undergoes impact, e.g.,falling, etc., since the holding insulator 96 b functions as a buffermaterial with respect to the lead wire 90 and/or the temperature fuseelement 97, it can be suppressed that connection between the lead wire90 and the connecting portion 87 of the lead terminals 82 a, 82 b may bebroken, and/or the temperature fuse element may be damaged.

The temperature fuse element 97 is disposed at dead space provided atthe battery modules 85 a, 85 b through the insulator 96 b. Thetemperature fuse element 97 is a protection element that in the casewhere the battery modules 85 a, 85 b are placed in over-charge state, orover-discharge state owing to, e.g., erroneous operation of the batterypack 80, the temperature fuse element 97 detects temperatures of thebattery modules 85 a, 85 b to interrupt current when temperature reachesa predetermined value so that over-charge or over-discharge proceeds nolonger.

Moreover, at the battery pack 80, there is attached, on the outercircumference of the accommodating case 4, a label 98 in which e.g.,manufacturing lot No. is indicated to thereby clarify source, etc. ofthe battery modules 85 a, 85 b and/or the circuit wiring board 83, etc.

It is to be noted that, at the battery pack 80, similarly to theabove-described battery pack 1, there may be provided battery partitionwall capable of preventing that battery modules 85 a, 85 b collide witheach other therewithin, and/or battery holding piece for permitting thebattery modules 85 a, 85 b to be accommodated therewithin withoutshaking, etc.

Also in the battery pack 80 of the configuration as stated above, leadterminals 82 a, 82 b are welded to both end surfaces of the battery 81at the battery modules 85 a, 85 b in the state where connectingreliability has been enhanced (improved). Thus, it is possible toprevent an inconvenience such that connection between the battery andthe lead terminal is broken at the connecting portion so that thebattery pack becomes unavailable or unusable, which takes place as theresult of the fact that impact is applied from the outside as in theprior art.

Moreover, even in the battery pack 80, since electric resistance valuesof the lead terminals 82 a, 82 b are caused to be small, it is possibleto prevent an inconvenience such that temperature fuse 97, etc. providedwithin the pack becomes operative by heat by electric resistance of thelead terminal in allowing large current to flow as in the prior art sothat charge/discharge operation cannot be performed. Accordingly, evenin the battery pack 80, it is possible to perform charge/dischargeoperation by so-called large current for allowing current of the orderof 1 C to 2 C per battery to flow, for example.

It should be noted that while explanation has been given in theabove-described examples by taking example of cylindrical lithium ionsecondary battery as the battery 2, the present present invention is notlimited to such an implementation, but can be applied to primary batteryand/or polymer battery, etc. in which lead terminal is attached toexternal terminal irrespective of shape, e.g., rectangular type battery,thin type battery, coin type battery and/or button type battery, etc.

It is to be noted that while the present invention has been described inaccordance with certain preferred embodiments thereof illustrated in theaccompanying drawings and described in detail, it should be understoodby those ordinarily skilled in the art that the invention is not limitedto embodiments, but various modifications, alternative construction orequivalents can be implemented without departing from the scope andspirit of the present invention as set forth by appended claims.

INDUSTRIAL APPLICABILITY

As described above, in accordance with the present invention, theportion in which the thickness of the lead terminal is thin is welded tothe external terminal of the battery, thereby making it possible to weldthe lead terminal in the state where the connecting reliability has beenenhanced (improved). From this fact, e.g., when impact is applied fromthe external portion, it can be prevented that connection between leadterminal and battery is broken at welding portion. Moreover, inaccordance with the present invention, the portion in which thickness islarge of the lead terminal serves to reduce electric resistance of thelead terminal taking place by current flowing in plane direction of thelead terminal. Accordingly, in accordance with the present invention,since heat by electric resistance when current flows in the leadterminal is suppressed, it can be prevented that the batterycharacteristic may be deteriorated by heat of the lead terminal heatedby current at charge/discharge operation. Further, in accordance withthe present invention, since there is provided power supply apparatus inwhich energy loss by voltage drop of electric resistance when currentflows in the lead terminal has been suppressed, it is possible toelongate drive duration time of electronic equipments, etc.

1. A lead terminal for electrically connecting a first connected bodyand a second connected body, the lead terminal comprising: a weldingportion in which electricity is caused to flow in the state caused to bein contact with an external terminal of the first connected body so thatthe welding portion is resistance-welded to the external terminal of thefirst connected body; a connecting portion connected to an externalterminal of the second connected body; and a conductive portionpositioned between the welding portion and the connecting portion, andserving to allow these portions to electrically conduct, wherein thelead terminal is a laminated material having at least a first conductivelayer of a first conductivity and a second conductive layer of a secondconductivity, and wherein the welding portion is constituted only by thefirst conductive layer that has a lower conductivity than the secondconductive layer, and wherein the welding portion is formed so that itsthickness is thinner than thickness of the conductive portion.
 2. Thelead terminal as set forth in claim 1, wherein plural welding portionsare provided as the welding portion.
 3. The lead terminal as set forthin claim 1, wherein the welding portion is a recessed portion providedat positions opposite to each other of both principal surfaces of theplate material, or a predetermined position of one principal surface ofthe plate material.
 4. The lead terminal as set forth in claim 1,wherein in the case where plural welding spots (points) of the weldingportion and the external terminal of the first connected body areprovided, a slit or slits is or are formed between these welding spots.5. The lead terminal as set forth in claim 1, wherein the connectingportion is formed so that its thickness is thinner than the thickness ofthe conductive portion.
 6. The lead terminal as set forth in claim 1,wherein the conductive metal contains any one kind or plural kinds ofnickel, nickel alloy, iron, iron alloy, stainless steel, zinc, zincalloy, copper, copper alloy, silver, silver alloy, gold, gold alloy,platinum, platinum alloy, aluminum, aluminum alloy, molybdenum,molybdenum alloy, tungsten, tungsten alloy, titanium, titanium alloy,chromium, chromium alloy, zirconium, zirconium alloy, beryllium,beryllium alloy, rhodium, and rhodium alloy.
 7. The lead terminal as setforth in claim 1, wherein the conductive portion is formed by alaminated body in which plural layers of a first conductive metal havinga first conductivity and plural layers of a second conductive metalhaving a second conductivity are laminated.
 8. The lead terminal as setforth in claim 7, wherein the welding portion consists of the firstconductivity metal having the first conductivity lower than the secondconductivity.
 9. The lead terminal as set forth in claim 7, wherein thefirst conductivity metal contains any one kind or plural kinds ofnickel, nickel alloy, iron, iron alloy, stainless steel, zinc, and zincalloy, and the second conductivity metal contains any one kind or pluralkinds of copper, copper alloy, silver, silver alloy, gold, gold alloy,platinum, platinum alloy, aluminum, aluminum alloy, tungsten, tungstenalloy, beryllium, beryllium alloy, rhodium, and rhodium alloy.
 10. Thelead terminal as set forth in claim 7, wherein the laminated body is aclad material in which the first conductivity metal and the secondconductivity metal are pressurized while heating these metals in thestate where they are laminated to thereby laminate and connect the firstconductivity metal and the second conductivity metal.
 11. The leadterminal as set forth in claim 7, wherein the laminated body is alaminated wood (plywood) in which the first conductivity metal and thesecond conductivity metal are pressurized while heating these metals inthe state where they are laminated through conductive adhesive agent orfilm-shaped low melting point conductive metal therebetween so that thefirst conductive metal and the second conductive metal are laminated andconnected.
 12. The lead terminal as set forth in claim 7, wherein thelaminated body is a laminated wood (plywood) in which the firstconductive metal and the second conductive metal are welded to eachother in the state where they are laminated to thereby laminate andconnect the first conductivity metal and the second conductivity metal.13. The lead terminal as set forth in claim 1, wherein the lead terminalis provided over a range from one edge end of the conductive portiontoward opposite other edge end, and is bendable at a bending portionformed so that its thickness is thinner than thickness of the conductiveportion.
 14. The lead terminal as set forth in claim 1, wherein thefirst connected body is a battery, and the welding portion is welded tothe external terminal of the battery.